Crunchbase - Crunchbase is a platform for discovering industry trends, investments, and news about companies around the world.

Hunter - Find all the email addresses related to a domain

CB Insights - CB Insights is a company database for the venture capital and corporate development community.

Apollo.io - Apollo’s predictive prospecting, sales engagement, and actionable analytics help the teams to reach its full revenue potential.

Tracxn - data on companies

Icypeas - This email finder has the capacity to bypass catch-alls